diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1941cb21..9c57a84d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,9 @@
 
 ### Fixed
 
+- **mcpplibs.mwrap.meshoptimizer 1.3.1（包装修订 1）。** 库以 `-ffp-contract=off`、不开 fast math 编译：同样的输入在每个平台上逐位得到同样的
+  meshlet、聚类与简化结果。1.3 按平台默认编译，arm64 把乘与加合成一次舍入，打乱的 48 × 48 网格得到的 meshlet 与 x86-64 不同（由一个
+  消费者在 ubuntu-24.04-arm 上的测试发现）。上游源码不变；消费者测试 `tests/mwrap/meshoptimizer-simplify` 改用 1.3.1。
 - **mtest 0.8.5.** 四个包的 0.8.5（同一标签、同一归档）：`e2e::run` 的结果在输出达到上限时如实说明——`outcome` 带回
   `out_truncated`、`err_truncated` 与 `held_open`，`command` 可声明各输出的上限（`out_limit`、`err_limit`，默认值不变），
   失败的 `succeeded`、`exited` 指出被截断的输出及其长度（mcpp-community/mtest#22）。其余行为不变。
diff --git a/pkgs/mwrap/meshoptimizer.lua b/pkgs/mwrap/meshoptimizer.lua
index 1eed8b5b..65187bb5 100644
--- a/pkgs/mwrap/meshoptimizer.lua
+++ b/pkgs/mwrap/meshoptimizer.lua
@@ -1,4 +1,4 @@
--- Immutable upstream-aligned mwrap source release (meshoptimizer-m mwrap-1.3);
+-- Immutable upstream-aligned mwrap source release (meshoptimizer-m mwrap-1.3, mwrap-1.3.1);
 -- GLOBAL and CN bytes are identical.
 --
 -- The wrapper is Apache-2.0; the library it vendors and links statically,
@@ -27,6 +27,13 @@ package = {
                 },
                 sha256 = "5172030f7b27b757cff2945d661e12969a191b08ed8b8ce19e70220fd3654e7e",
             },
+            ["1.3.1"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/meshoptimizer-m/releases/download/mwrap-1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/mwrap-meshoptimizer/releases/download/1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                },
+                sha256 = "663638294c4e54cb37fce138019c5d597e07ee8df25ab11dfa75ff2d772a37d4",
+            },
         },
         macosx = {
             ["1.3"] = {
@@ -36,6 +43,13 @@ package = {
                 },
                 sha256 = "5172030f7b27b757cff2945d661e12969a191b08ed8b8ce19e70220fd3654e7e",
             },
+            ["1.3.1"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/meshoptimizer-m/releases/download/mwrap-1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/mwrap-meshoptimizer/releases/download/1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                },
+                sha256 = "663638294c4e54cb37fce138019c5d597e07ee8df25ab11dfa75ff2d772a37d4",
+            },
         },
         windows = {
             ["1.3"] = {
@@ -45,6 +59,13 @@ package = {
                 },
                 sha256 = "5172030f7b27b757cff2945d661e12969a191b08ed8b8ce19e70220fd3654e7e",
             },
+            ["1.3.1"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/meshoptimizer-m/releases/download/mwrap-1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/mwrap-meshoptimizer/releases/download/1.3.1/meshoptimizer-m-1.3.1.tar.gz",
+                },
+                sha256 = "663638294c4e54cb37fce138019c5d597e07ee8df25ab11dfa75ff2d772a37d4",
+            },
         },
     },
 }
diff --git a/tests/mwrap/meshoptimizer-simplify/mcpp.toml b/tests/mwrap/meshoptimizer-simplify/mcpp.toml
index 31422da0..bcb574aa 100644
--- a/tests/mwrap/meshoptimizer-simplify/mcpp.toml
+++ b/tests/mwrap/meshoptimizer-simplify/mcpp.toml
@@ -8,4 +8,4 @@ description = "Consume the immutable meshoptimizer wrapper: index a grid, order
 # An explicit empty table overrides the legacy workspace redirect.
 
 [dependencies]
-mcpplibs.mwrap.meshoptimizer = "1.3"
+mcpplibs.mwrap.meshoptimizer = "1.3.1"